After an acident in the research of parallel dimensions, a portal was opened and one of the researchers fell inside. He was successfully rescued, however the rescued scientist wasn't like before. While he looked the same from the outside, his body was nearly indestructible, his strength was immense, he could resist temperatures much higher than the sun's core and his brain and body could function and react normally at the speed of mach 50, allowing him to move faster than the human eye can see (these are the effects of becoming bound to the laws of another dimension, and having his body changed to fit said dimension, an event which wasn't reversed once he returned). In this question, I'm interested on his perception, especially since, in our own case, we have the feeling that things are happening in slow motion in some cases of flight or fight situation, despite the rate at which time passes not having changed.

With a brain and eyes that react to the world at mach 50, to what extent would the world look like it's in a slow motion, based on the perception speed of the normal eye from an average human? I'm having problems estimating how exactly would he see, and that's important to determine how he'll react to the world around him.

Note/edit: the character is not trapped in a different time rate, but "merely" has a body capable of processing and reacting to information much faster than a human normally could, and ages at a normal human rate despite having a different body. Think of it as an extreme version of listening to a sped up version of a song many times and then suddenly listening to the normal one again, extended to his senses and with a muscular system capable of accompanying such thought speed.

  • $\begingroup$ We have several questions dealing with this scenario: worldbuilding.stackexchange.com/q/112390/30492 is one $\endgroup$
    – L.Dutch
    Apr 25, 2020 at 14:16
  • 1
    $\begingroup$ @L.Dutch - Reinstate Monica♦ thanks for the example, but mine isn't quite the same. While the asker is interested in the effects of a predetermined perception of time to the characters behavior, I'm one step back, being more interested in how the increased speed affects character's perception of time. $\endgroup$ Apr 25, 2020 at 14:47

2 Answers 2


You don't define exactly what's happening at Mach 50. Let's say that his maximum running speed is Mach 50, and see where that gets us.

That gives him a maximum speed of 50 * 340 = about 17,000 metres per second. A really good sprinter can do 100 metres in 10 seconds, or 10 metres per second. So he's going about 1,700 times faster than a normal human, at a conservative estimate.

He has several major problems:

  • He needs to eat and drink at 1,700 times the rate of normal people. This will take a bit of organising, and there's very little time: six minutes of normal time is a week for him, when the effects of starvation start to kick in. He's going to have to go out and steal, and he may have trouble getting enough water out of normal plumbing.
  • Boredom. Normal slow-motion is less than a ratio of 10. He's going hundreds of times faster than that. He can't communicate except in writing, and this will get very frustrating.
  • Damage to everything around him. With care, he can move slower than the speed of sound, but it takes a lot of care. Slow, deliberate stepping for a normal person is half a metre per second, a twentieth of a fast sprinter. Moving at the same pace in his accelerated time still leaves him moving at Mach 2.5. The supersonic shockwaves that something as big as a person moving at that speed makes will blow out windows, deafen and shred the clothing of everyone nearby, and generally make life difficult. However, this problem won't last long.
  • He'll die of old age fairly soon. If he's 25, and due to live another 65 years, that will last him just under two weeks of ordinary people's time.

Can I suggest using a slower time rate? A factor of two or three still makes him superhuman, and is far easier to cope with.

  • 4
    $\begingroup$ Forget running. With his speed any normal body movements, like blinking his eyes, cause enough air-friction to envelop him in clouds of superheated air plasma. He may be indestructible but everything around him will be on fire. $\endgroup$
    – Tonny
    Apr 25, 2020 at 16:26

This can go in at least 3 ways:

  1. Constant brain speed-up. The entire brain is always working in a high speed mode. This way every normal events like speech and gestures would be perceived in super slow motion. The speedster needs to adapt to this disparity and learn to listen and speak very, very slowly;

  2. Speed bursts. When at rest, the brain works at regular, humane speed. The speedster is essentially not a speedster at that time. But when he moves, the brain functions are quickening to match his speed. In "turbo" mode he won't likely be able to communicate with regular people, but at all other times he would be a normal, "slow" person.

  3. "Spinal" reflexes. The brain is not sped up uniformly. While functions responsible for the motion and vision are super fast, regular thinking always goes at normal pace. So the speedster would say "I need to go from New York to Washington!", and run there in less than a minute, all without making a single misstep. But this trip, according to his own perception, would be just one blur.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .